Mesangial cells from transgenic mice with progressive glomerulosclerosis exhibit stable, phenotypic changes including undetectable MMP-9 and increased type IV collagen.

Mice transgenic for bovine growth hormone (bGH) develop progressive mesangial sclerosis resulting in uremia. Mesangial cells from bGH mice were isolated to determine whether the cells maintained a stable phenotypic change in the synthesis and degradation of extracellular matrix, which contribute to the glomerular lesions in vivo. The bGH mesangial cells were 1.2-fold larger than cells from control mice. They had a 1.7-fold increase in doubling time, a 7-fold decrease in labeling index (p < 0.0001), and a 2.4- and 2-fold decrease in c-myc (p < 0.05) and insulin-like growth factor I gene expression, respectively. Collagen synthesis and degradation were studied by PCR, ELISA, and gelatin zymography. bGH mesangial cell alpha 1 collagen IV mRNA levels were increased 2.3-fold (0.47 +/- 0.25 versus 0.20 +/- 0.09 attomoles/500 cells, p < 0.01) whereas secreted collagen IV and collagen IV in the cell lysates were increased 1.4-fold (25.1 +/- 5 versus 17.2 +/- 4 ng/ml/10(5) cells) and 1.8-fold (30.5 +/- 3 versus 16.7 +/- 3 ng/ml/10(5), p < 0.05), respectively. There were no differences in collagen I mRNA levels or in the protein content of either the media or cell lysates. We were not able to detect metalloproteinase 9 (MMP-9) mRNA expression or MMP-9 protein in bGH mesangial cell medium, whereas both mRNA and protein were present in controls. MMP-2 mRNA and enzyme activity in bGH cells were, however, elevated 1.5-fold (p < 0.05) and 2.1-fold (p = 0.05) over controls. Transforming growth factor beta 1 mRNA in bGH cells was 1.6-fold higher than that of controls (p < 0.05). The data suggest that (a) mesangial lesions may result from stable, genetically induced, phenotypic changes in mesangial cells, and (b) alterations of MMP-9 and collagen IV expression by mesangial cells may contribute to an imbalance between extracellular matrix synthesis and degradation and play a critical role in the genesis of glomerulosclerosis.